Oxidation is one of the most fundamental transformations in organic synthesis and there are numerous methods reported in the literature. (Hudlicky, M. "Oxidations in Organic Chemistry" ACS Monograph 186, 1990.) However, direct conversion of primary alcohols to the corresponding carboxylic acids is still a challenge especially in the presence of other functional groups. There are only a few commonly used methods for this transformation including CrO.sub.3 /H.sub.2 SO.sub.4 (Bowden; Heilbron; Jones; Weedon J. Chem. Soc., 1946, 39; Bowers; H.; Jones; L. J. Chem. Soc., 1953, 2548; Millar, J. G.; Oehlschlager, A. C.; Wong, J. W. J. Org. Chem. 1983, 48, 4404.), RuCl.sub.3 /H.sub.5 IO.sub.6 (Carlsen, P. H. J.; Katsuki, T.; Martin V. S.; Sharpless, K. B. J. Org. Chem. 1981, 46, 3936.) and TEMPO/NaClO (Nooy, A. E. J. de; Besemer, A. C.; Bekkum, H. v. Synthesis, 1996, 1153.; Anelli, P. L.; Biffi, C.; Montanari, F.; Quici, S. J. Org. Chem. 1987, 52, 2559.; Miyazawa, T.; Endo, T.; Shiihashi, S.; Okawara, M. J. Org. Chem. 1985, 50, 1332). A two-step process involving Swern oxidation (Mancuso, A. J.; Huang, S-L., Swern, D. J. Org. Chem. 1978, 43, 2480.; Mancuso, A. J.; Brownfan, D. S.; Swern, D. J. Org. Chem. 1979, 44, 4148.; Ireland, R.; Norbeck, D. J. Org. Chem. 1985, 50, 2198.) followed by oxidation of the resulting aldehyde with NaClO.sub.2 (Lindgren, B. O.; Nilsson, T. Acta Chem. Scand. 1973, 27, 888.; Dalcanale, E.; Montanari, F. J. Org. Chem. 1986, 51, 567) is another option. However, all of these procedures have limitations and disadvantages, and new methods for the oxidation of primary alcohols to the carboxylic acids are still desired. (Schroder, M.; Griffith, W. P. J. Chem. Soc. Chem. Comm. 1979, 58.; and Paquette, L. A.; Dressel, J.; Pansegrau, P. D. Tetrahedron Lett. 1987, 28, 4965. )
A very facile oxidation of primary alcohols to carboxylic acids using only catalytic CrO.sub.3 and periodic acid (H.sub.5 IO.sub.6) as the stoichiometric oxidant is described. Although chromium catalyzed oxidation of secondary alcohols is known, (Muzart, J. Chem. Review 1992, 92, 113-140; and Muzart, J. and Piva, O. Tetrahedron Lett. 1988, 29, 2321-2324.) a similar version for the oxidation of primary alcohols to the acids has not been reported. This chromium catalyzed oxidation method avoids the chromium disposal issues associated with running a typical Jones oxidation reaction, reduces the epimerization of any .alpha.-chiral centers, oxidizes secondary alcohols to the corresponding ketones in quantitative yield, and is a one step procedure. The reaction is mild, rapid, high yielding and only requires 1-2 mol % of CrO.sub.3.
The present invention discloses a process for preparing a compound of Formula I: ##STR3## comprising reacting a compound of Formula II, ##STR4## in a solvent with periodic acid and a catalytic amount of a chromium reagent to oxide to the compound of Formula I.